Semiconductor wafer processing is sometimes performed in batches, with all wafers in a cassette being subjected to a process simultaneously. However, single water processing is becoming more prevalent because point to point process variations in a single water processing apparatus can usually be controlled more precisely. In single wafer processing, wafers are usually moved by automated handlers from cassettes to a water chuck and back again. In some cases, the wafer sits on the chuck, held in place only by gravity. In other cases, the wafer is held either by applying a vacuum to one or more backside areas of the water through holes in the chuck (e.g., a “vacuum chuck”) or by applying a voltage to a chuck that is formed of an insulator overlying a conductor (e.g., an “electrostatic chuck” (ESC)). Processing may involve controlling the temperature of the chuck and thus the wafer. Certain chucks have both heating and cooling capability, while others have only heating capability. Chucks can be heated by running a heated fluid through the chuck or by passing current through a resistive heater element integrated with the chuck.
Heating capability for a wafer chuck is often implemented by forming resistive heater traces on the chuck. Presently, such heater traces are often fabricated using thick film technologies such as screen printing, ink jet printing or other liquid dispensing techniques. In these techniques, forming precise lines and corners, as well as forming layers with precise thickness control, can be challenging.